Trifluoromethylated aromatic compounds have a number of important utilities. They find use as herbicides, pesticides and fungicides. Certain of these compounds are pharmaceutically active. There is a continuing need to produce trifluoromethylated aromatic compounds in an efficient and inexpensive manner, using readily available starting materials.
Trifluoromethylation is known in the art and has been practiced commercially by, for example, treating trichloromethyl benzene with hydrogen fluoride over a metal catalyst. It is desirable to avoid use of hydrogen fluoride, which is corrosive and extremely dangerous.
It is also known to carry out trifluoromethylation using fluorinating agents which already contain the trifluoromethyl group, such as trifluoromethyl iodide or bis(trifluoromethyl)mercury. Such processes involve use of expensive starting materials, and the processes themselves are difficult and produce significant amounts of undesired byproducts.
U.S. Pat. No. 4,895,991 teaches the preparation of trifluoromethyl organometallic reagents from dihalodifluoromethanes. A copper reagent is prepared by reacting the zinc or cadmium organometallic compound with cuprous bromide. Preparation of trifluoromethyl aromatics in solution is disclosed using DMF, metallic copper or copper-bronze, aromatic iodide, and CF.sub.2 BrX, where X=Br or Cl.